I. Field of the Invention
This invention relates generally to a manhole and catch basin extension. More particularly, it relates to a plastic extension that may be used to elevate a manhole cover support frame or a catch basin grating support frame, thereby elevating the top surface of a manhole or catch basin to a desired level and angle such that, for example, the level of a newly surfaced or resurfaced roadway and the level of the manhole cover or catch basin grating are the same.
II. Discussion of the Prior Art
It is common practice to construct a manhole in roadways or streets to allow access to underground, sanitary and storm sewers and utility conduits. When a manhole in a roadway is first constructed, it comprises a base with concentric sides extending upward, a cone mounted above the base (usually a monolithic cast), of usually a tubular, conical, or cylindrical structure made of concrete or brick, a cast iron support frame and a cover. The cast iron support frame is positioned above the cone and supports the manhole cover. The concrete manhole structure is built up to an elevation approximately that at which the manhole cover will be at road level. One or more spacers may then be used between the cast iron support frame and cone, to ensure that the cover will be flush with the road surface.
It is also common practice to construct a catch basin along the curb line of roadways or streets to allow surface water drainage into underground storm sewers. The catch basin structure is similar to the manhole structure. The catch basin, when first constructed, comprises a base with concentric sides extending upward, a cone resting above the base with a rectangular, cylindrical, oblong, etc. cross-section on which is mounted a cast iron support frame that supports a grating. Sometimes, a rectangular top slab may be positioned directly above the cone. The rectangular top slab is used to narrow the opening in the cone and supports either a rectangular or concentric cast iron support frame. The catch basin structure is also built up to an elevation such that the grating will be approximately at road level, with rectangular spacers being employed to ensure that the grating will be at grade level.
From time to time, roads are required to be resurfaced. When the road is resurfaced, a layer of paving material is deposited over the existing pavement. Consequently, the manhole cover and grating level will be below the top surface of the new pavement. At the time that the road is resurfaced, the manhole cover and grating must also be raised to the new level to avoid having a recess in the roadway. These recesses produce unwanted bumps and shock to vehicles passing over the depression and also create sites where water can collect. Freezing of such water can result in damage to the road resurfacing material.
Occasionally, the manhole and catch basin are constructed on a hillside. Usually, the bases are aligned vertically with the earth's gravitational line, not perpendicular to the surface or the hillside's vertical line. To avoid having a recess (pothole) in the roadway, the manhole cover and grating must be supported at an angle to the bases, equal to the angle between the gravitational line and the hillside vertical line. Thus, a need exists to efficiently change the angle of the manhole cover and grating to be flush with the resurfaced roadway.
The prior art has recognized a need to efficiently raise the level of the manhole flush with the resurfaced roadway. To meet this need, a variety of adapter rings and adjustment rings have been introduced, such as that described in U.S. Pat. No. 5,205,668. Each ring is arranged to rest on the upper rim of the cast iron support frame. Further, these adapter or adjustment rings include an annular lip on which the manhole cover can rest, raising the level of the manhole. These rings can be stacked or adjusted to provide varying heights. A disadvantage to these rings is that severe loadings tend to move them and cause the cover to become unstable and rock. Bolting the cover, adapter ring and the support frame together will prevent the cover from rocking, but the bolts, over time, become rusted and difficult to remove, requiring the entire unit to be replaced when a second resurfacing operation takes place.
Even with adapter rings available, U.S. Pat. No. 5,205,668 and U.S. Pat. No. 4,188,151 recognize that, rather than using adapter rings, it is still a common practice to remove the existing pavement around the manhole and increase the height of the manhole cover by placing support materials, such as bricks, on the cone top surface and then placing the support frame on top of the bricks. The disadvantage of this continued procedure is that laying mortar and brick is expensive and time-consuming. Thus, a need exists for a relatively inexpensive, rigid, lightweight spacer to be placed between the support frame and the cone top surface to raise the level of either the manhole cover or catch basin grating.
The present invention overcomes these disadvantages by providing a relatively inexpensive, sturdy, lightweight plastic spacer that is aligned between the cone top surface and the support frame. The plastic spacer member may also be aligned between the top slab and the support frame. One or more of such plastic spacers, having a high compressive strength, are quickly and easily stacked atop the cone top surface with the uppermost plastic spacer forming the surface on which the cast iron support frame rests. An adaptable wedge is provided that allows the manhole cover or grating to be supported at an angle relative to the top slab or cone. This change in angle allows the cover or grating to remain flush with a resurfaced roadway located on a hillside.